Insulating a Floor

Insulating a floor will be most beneficial to homeowners where the floor is above a cold space. A cold space is any unheated or unused room as these can cause buildings to lose a lot of heat very quickly. Bedrooms above garages and houses with basements or cellars are the most common examples of this. These types of rooms often mean the room above it has suspended floors, which can be extremely easy to install floor insulation for. It’s widely accepted that floors that are solid, usually concrete, are harder to insulate and costlier to insulate. Floor insulation is something that can be done by most homeowners without the need to call in a professional. It is recommended however that you bring in a qualified electrician if when installing floor insulation, you need to move electric sockets to raise them higher.

1. Insulating a suspended floor

2. Insulating a solid floor

3. Other tips for insulating a floor

Floor Insulation for Suspended Floors

To identify if you have a suspended floor you need to assess whether there is a void beneath your floorboards and the floorboards themselves are resting over joists. This void can cause a lot of heat loss if it’s not addressed so filling this void with floor insulation such as insulation roll or insulation board can minimise household bills and make your home more comfortable too.

insulation-nettingSuspended floor insulation is the easiest to fit when there is a cellar or basement beneath the property. This should give easy access to the void below the joists, so insulation can be fixed in place using insulation netting. insulation slab or insulation board can be friction fit into the joists so that the insulation stays put whilst insulation netting is rolled out and fixed at each joist just for some extra support. By pulling the netting taught and ensuring the insulation is tightly packed into the space you can reduce heat loss through the floor without needing to lift a single floorboard.

Unfortunately, if your home doesn’t feature a basement or a cellar, but the floor is still suspended, floorboards and any floor finishings will need to come up. Since it’s a big job to empty a room of furnishings to gain access to the void below, we recommend that this is done alongside other big jobs like plastering or painting.

Like insulating a floor where a basement or cellar provides access to the joists, you need to lift the floorboards and put them to one side before laying rigid insulation boards in the joist spaces. Cut each piece of insulation board to just slightly smaller than the joist space you’re going to fit it into, this will provide friction for a tight fit, so no air can escape through the side gaps.

You can use insulation roll like popular natural insulation sheep's wool by fitting inexpensive insulation netting underneath the joists as in the picture to the right. Drape the netting as low as needed to accommodate the thickness of the insulation roll then roll the insulation out as usual, taking care to make sure it extends to the width of the joists.

Please be aware of airbricks in outside walls. Floorboards will rot if airbricks are covered as there will be no ventilation! These should be at least 2 inches below the bottom of the insulation before the hardcore.

insulation-board insulation-netting insulation-slab natural-insulation

Floor Insulation for Solid Floors

Solid floors in theory shouldn’t need as much insulation as suspended floors as they’re thicker and harder for heat to escape through. Stone floors can be as much as 50cm thick in old builds! However some heat can still be lost through these types of floors so it’s good to assess the options and weigh up the benefits of a warmer, more efficient floor.

Obviously with a solid floor you’re unable to remove the floor to insulate so the only method of insulating a floor is to layer up. It’s advisable to install a damp proof membrane between the solid floor and the insulation to ward off any unwanted moisture. Wet insulation is even more inefficient than no insulation at all!

With the use of specialist build ups with acoustic matting and underlays, you can reduce echoes and airborne noise in buildings that are built from solid walls and typically spacious inside like older churches that either need insulating or are being converted. For example, once insulation board has been laid across a solid floor, install a 1.2mm thick layer of acoustic barrier mat followed by a 9mm thick layer of acoustic MDF sheet to reduce the airborne noise and echoes whilst adding just 10.2mm to the floor thickness.

One thing that’s very important to consider is the floor level. With a minimum of three layers going on top of the existing solid floor, that can impact the height of the internal floor and affect other fixtures and fittings. It may be appropriate to trim doors to size and to employ an electrician to raise electric sockets.

Damp-Proof-Membrane Chipboard acoustic-barrier-mat acoustic-mdf-sheet

What else can I do to insulate a floor?

Gaps between floorboards and around skirting boards can allow heat to escape and cause a draft. Avoid this for just a few pounds by going around the edges with a moisture-resistant sealant.

Here at Insulation Superstore we have experienced advisors that can offer sound and sensible advice in regards to your project. Trained by manufacturers with the technical knowledge required to assist you, contact our advisors with build specifications, a blueprint of what you're looking to achieve, or even just a broad idea of what your aim is. Contact our advisors by using our live chat in the bottom right hand corner or by phoning us on 01752 692 206.